syslinux
All the configurable defaults in SYSLINUX can be changed by putting a file called syslinux.cfg.
SYSLINUX searches for the SYSLINUX.CFG file in the following order:
/boot/syslinux/syslinux.cfg /syslinux/syslinux.cfg /syslinux.cfg
Here is a simple example syslinux.cfg file, with one entry to boot a Linux kernel:
DEFAULT linux LABEL linux SAY Now booting the kernel from SYSLINUX… KERNEL vmlinuz.img APPEND ro root=/dev/sda1
see http://syslinux.zytor.com/wiki/index.php/SYSLINUX for the complete documentation.